Closure cap for a container

ABSTRACT

In a closure cap (1) of thermoplastic material, produced by an injection moulding process, the guarantee strip (2) which is formed integrally thereon is provided, at the lower edge (2) of the closure cap, on the outside (6), with a reinforcement portion (5) which is disposed between two desired-rupture connecting web portions (3). Besides the advantages, which are already known, of a reinforcement portion on the guarantee strip, the reinforcement portion according to the invention serves as a support for bearing against the moulding tool in order to prevent stretching of the connecting web portions (3) or deformation of the guarantee strip (2) when the cap is removed from the mould.

The invention relates to a closure cap for a container, the cap being ofthe type which is provided with a heat-shrinkable guarantee strip and isproduced integrally with the guarantee strip from thermoplastic materialin an injection molding process, wherein the guarantee strip isconnected to the lower edge of the closure cap by way of a plurality ofrupturable connecting web portions and is intended at least partially toembrace the neck of the container and can be brought into engagementtherewith by heat-shrinking, and wherein the wall thickness of theguarantee strip has a reinforcement portion in the region between eachtwo rupturable connecting web portions and the individual reinforcementportions are interrupted and spaced apart by portions of smaller wallthickness.

A closure cap of the kind indicated above is described for example inthe European patent publication No. 34,997, published on Sept. 2, 1981.In accordance with that specification, the guarantee strip is providedon the inward side with a chord-like reinforcement, the purpose of whichis to enhance the flow behaviour of the thermolastic material in theinjection moulding operation. In addition, the reinforcement is intendedto facilitate the operation of shrinking the guarantee strip on to theneck of the container by means of the effect of heat.

It has now been found that the dimensions of the reinforcement on theinward side of the guarantee strip can only lie within a restrictedrange as in that respect the dimensions and the configuration of theneck of the container must be taken into account. In addition, problemsstill occur when removing the closure cap from a moulding tool whichopens in an axial direction, but those problems are not directly relatedto the reinforcement on the guarantee strip. More specifically, whenstripping the closure cap from the inner tool portion, the guaranteestrip is subjected to forces which act in the opposite direction to thedirection of ejection from the mould and which pull the guarantee stripdownwardly. As a result of that, undesirable stretching occurs at theconnecting web portions which form the desired rupture locations, as thethermoplastic material is still relatively hot and stretchy after theinjection moulding operation. On being removed from the mould, theguarantee strip may be deformed in particular in the region between twodesired-rupture connecting web portions, in such a way that it is nolonger capable of being brought into proper engagement with the neck ofthe container.

The object of the present invention is therefore to provide a closurecap of the kind set forth in the opening part of this specification,wherein the thickened portion on the guarantee strip can be betterdimensioned in accordance with the requirements involved, and wherein inaddition the operation of removing the cap from the injection mouldingtool can be carried out without damaging or causing deformation of theguarantee strip.

In accordance with the invention, that object is achieved by a screw capwhich includes the features that the reinforcement portions are arrangedon the outward side of the guarantee strip, and the cross-sections ofthe reinforcement portions increase toward the lower edge of theguarantee strip.

By virtue of the reinforcement portion being disposed on the outwardside of the guarantee strip, the reinforcement portion can be made oflarger dimensions, as required, than would be possible in the case of areinforcement portion disposed on the inward side of the guaranteestrip. As will be described in detail hereinafter, the reinforcementportion also serves as an aid to stripping the cap out of the injectionmoulding tool, insofar as the guarantee strip itself is retained in thetool by the reinforcement portion upon relative movement of the internalmandrel. The fact that the cross-section of the reinforcement portionincreases towards the lower end of the guarantee strip provides that theguarantee strip bears against the tool when the cap is stripped from theinternal mandrel, but that nonetheless the step of ejecting the closurecap in the opposite direction is not made unnecessarily difficult.

Good properties in regard to shrinkability of the guarantee strip andthe flow properties of the injection moulding material are achieved ifthe reinforcement portion is of substantially square or rectangularconfiguration in plan and extends over a sector which is equal to orsmaller than half the sector between two desired-rupture connecting webportions. In some situations of use, it may also be advantageous for thereinforcement portion to be of a substantially triangular configuration,with one side of the triangle extending substantially parallel to thebottom edge of the guarantee strip.

There is also disclosed an apparatus for producing a closure cap of thekind set forth, which is simple in manufacture and which producesfault-free closure caps at high rates of output. Such an apparatuscomprises an upper tool portion for forming the outside contour of theclosure cap, a lower tool portion for forming the lower edge of theclosure cap and the outside of the guarantee strip, wherein the plane ofcontact of the upper and lower tool portions lies in the plane of thelower edge of the closure cap, and comprising an inner tool portion forforming the internal contour of the closure cap and the inside and thelower edge of the guarantee strips, recesses being provided in the lowertool portion on the wall portion forming the outside of the guaranteestrip, a respective recess being disposed between each two connectingweb portions. The recesses may be relatively easily provided on alreadyexisting injection molding tools so that surprising improvements both inthe injection molding tool itself and also in the closure cap may beachieved by a relatively simple measure.

Embodiments of the invention are described in greater detail hereinafterand illustrated in the drawings in which:

FIG. 1 shows a view in cross-section of part of a closure cap accordingto the invention, enlarged by a factor of ten,

FIG. 2 shows a view from below of part of the closure cap shown in FIG.1,

FIG. 3 shows a side view of a reinforcement portion on the guaranteestrip,

FIG. 4 shows a side view of modified embodiment of a reinforcementportion on the guarantee strip,

FIG. 5 shows the closure cap of FIG. 1 in the injection moulding tool ina closed condition, and

FIGS. 6 to 11 show the operations involved in ejecting aninjection-moulded cap out of the tool, on a greatly reduced scale.

As shown in FIG. 1, a closure cap 1 is provided, as in per se knownmanner, with a guarantee strip 2 which is integrally connected to thelower edge 4 of the closure cap by way of desired-rupture connecting webportions 3. The closure cap illustrated also has a female screwthread 7for screwing on to the mouth opening of a container having a malescrewthread, together with a sealing lip 8 and an internal sealing means9. It will be appreciated that the closure cap may also be of adifferent configuration.

It is already known for the cross-section of the guarantee strip to beof a wedge-shaped configuration, with an angle α, because that makes itpossible to use tools which open in an axial direction. The guaranteestrip 2 is intended to be brought into engagement with a bead portion onthe neck of the container so that, when the closure cap 1 is unscrewed,the connecting web portions 3 tear, thereby indicating that the closurecap has already been opened once. In the case of a closure cap inaccordance with the illustrated construction, the guarantee strip isshrink fitted on to the neck of the container by the effect of heat.However, the configuration of the guarantee strip may also be altered insuch a way that, when the closure cap is screwed on, the guarantee stripcomes into engagement on the container, at the neck thereof, withoutbeing subjected to the effect of heat.

The configuration of the reinforcement portion 5 on the outward side 6of the guarantee strip can be seen from FIGS. 1, 2 and 3. Thecross-section of the reinforcement portion increases in a bead-likeconfiguration towards the lower edge 10 of the guarantee strip and is ofa wedge-like shape which is rounded off at the bottom, wherein, asillustrated, the wedge angle β of the reinforcement portion 5 issubstantially larger than the wedge angle α of the guarantee strip 2.The supporting action in the injection moulding tool, which isadditionally achieved with the reinforcement portion 5, can beparticularly clearly seen from FIG. 2. As viewed from below, thereinforcement portions 5 appear as segment-like projections which canbear against the tool, as can be seen in particular from FIG. 5.

The reinforcement portion may be of a square or rectangularconfiguration or approximately triangular, as shown in FIG. 4. In thatcase, the triangles may be of such a configuration that the tips thereofnearly touch, underneath the connecting web portions 3. Thereinforcement portions of square or rectangular configurationadvantageously extend over a sector A which is equal to or less thanhalf the sector B between two connecting web portions 3.

FIG. 5 shows the planes of separation of the various parts of the tool,in the region of the guarantee strip. The upper tool portion 11 definesthe external contour of the closure cap 1. The lower tool portion 12forms the lower edge 4 of the closure cap and the outward side 6 of theguarantee strip 2. In that arrangement, the lower tool portion 12 has aninternal wall surface 17 which flares conically downwardly at the wedgeangle of the guarantee strip. The plane of separation 13 between theupper tool portion 11 and the lower tool portion 12 is on the plane ofthe lower edge 4 of the closure cap 1. The internal contour of theclosure cap is formed by an internal tool portion 14 which also definesthe inward side 15 of the guarantee strip and the lower edge of theguarantee strip. When the closure cap is stripped off the tool portion14 by means of the lower tool portion 12, the closure cap itself issupported at the lower edge 4 thereof. The guarantee strip 2 in turn issupported separately by the reinforcement portions 5 which are formed byrecesses 16 in the material of the lower tool portion 12. By virtue ofthat arrangement, the forces applied to the guarantee strip as a resultof static friction when the tool portions are opened can no longerresult in the connecting web portions 3 being stretched or the guaranteestrip 2 being deformed. When the moulding material which reaches theguarantee strip by way of the connecting web portions 3 is injected, thereinforcement portions 5 cause the material to flow togetherhomogeneously in the region between two connecting web portions.

FIGS. 6 to 11 show the individual relative positions of the toolportions when the injection-moulded closure cap is being removed fromthe mould. Details of such an injection moulding tool are known to theman skilled in the art and will therefore not be described in greaterdetail herein. The movements of the individual parts of the tool areproduced by means of a hydraulic step-wise ejector 18.

In FIG. 6, all parts of the tool are closed so that they are in the samepositions as shown in FIG. 5. As illustrated in FIG. 7, the upper toolportion 11 is first raised so as to free the outside of the closurecap 1. In that operation, the closure cap 1 is retained by the innertool portion 14. The tool portion 14 comprises a plurality of componentswhich are concentrically fitted one into the other, as can beparticularly clearly seen from FIG. 8. That is necessary in order to beable to remove the complicated internal contour of the closure cap fromthe moulding tool. As shown in FIG. 8, the lower tool portion 12 isfirst raised somewhat, together with the inner tool portion 14, so thatthe internal sealing means in the closure cap 1 is released. In thatmovement, the guarantee strip 2 is still embraced by tool portions.

FIG. 9 shows the crucial phase in the operation of removing the mouldedcomponent from the tool, wherein the guarantee strip is removed from themoulding tool. The upper tool portion 12 is raised further so that theclosure cap, together with the guarantee strip, is stripped from theinner tool portion 14. In that operation, the guarantee strip issupported at the reinforcement portions or at the recesses, asillustrated in FIG. 5. When that phase is concluded, the closure cap 1is then only held by the lower tool portion 12.

In order for the closure cap to be entirely removed from the tool, apushrod 19 is extended, to eject the closure cap, as shown in FIG. 10.The pushrod 19 is preferably actuated pneumatically. After the closurecap is ejected, the individual tool portions move back into theiroriginal position so that the mould can be closed for a furtherinjection moulding operation. FIG. 11 shows the tool in the condition inwhich there is only the upper tool portion 11 that still has to beclosed.

I claim:
 1. A closure cap for a container, which cap is provided with aheat-shrinkable guarantee strip (2) and is produced integrally with theguarantee strip from thermoplastic material in an injection mouldingprocess, wherein the guarantee strip is connected to the lower edge (4)of the closure cap by way of a plurality of rupturable connecting webportions (3) and is intended at least partially to embrace the neck ofthe container and can be brought into engagement therewith byheat-shrinking, and wherein the wall thickness of the guarantee striphas a reinforcement portion (5) in the region between each tworupturable connecting web portions and the individual reinforcementportions are interrupted and spaced apart by portions of smaller wallthickness, including the improvement in that the reinforcement portions(5) are arranged on the outward side (6) of the gurantee strip (2) andthat the cross-sections of the reinforcement portions increase towardsthe lower edge of the guarantee strip.
 2. A closure cap according toclaim 1 characterised in that at least some of the reinforcementportions are of a substantially square or rectangular cross-section. 3.A closure cap according to claim 2 characterised in that at least someof the reinforcement portions on the guarantee strip extend over asector (A) which is equal to or smaller than half the sector (B) betweentwo connecting web portions (3).
 4. A closure cap according to claim 1characterised in that at least some of the reinforcement portions are ofa substantially triangular configuration in side view, wherein one sideof the triangle extends approximately parallel to the lower edge of theguarantee strip.